Fixed-abrasive chemical-mechanical planarization of titanium nitride

ABSTRACT

Titanium nitride layers planarized may be utilized in the production of integrated circuits, and various apparatus utilizing such integrated circuits. Planarizing solutions may be used for removing titanium nitride from the surface of a substrate using a fixed-abrasive planarizing pad. The planarizing solutions take the form of an etchant solution or an oxidizing solution. The etchant solutions are aqueous solutions containing an etchant and a buffer. The etchant contains one or more etching agents selective to titanium nitride. The oxidizing solutions are aqueous solutions containing an oxidizer and a buffer. The oxidizer contains one or more oxidizing agents selective to titanium nitride. In either solution, i.e., etchant or oxidizing solution, the buffer contains one or more buffering agents.

RELATED APPLICATIONS

This application is a Divisional of U.S. Ser. No. 10/116,585 filed Apr.4, 2002, which is a Divisional of U.S. Ser. No. 09/339,735 filed Jun.24, 1999 and issued as U.S. Pat. No. 6,419,554 on Jul. 16, 2002, whichapplications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to methods for planarizingsemiconductor substrates, and in particular to planarizing solutions andmethods of use for removing titanium nitride from the surface ofsemiconductor substrates using fixed-abrasive pads, and apparatusproduced therefrom.

BACKGROUND

Chemical-Mechanical Planarizing (CMP) processes are often used forforming a flat surface on a semiconductor substrate in the manufactureof electronic devices. CMP processes generally remove material from asubstrate surface to create a highly planar surface. A variety ofplanarizing machines have been developed to carry out such CMPprocesses.

Planarizing machines for use in CMP processing generally fall into twocategories: web-format and fixed-pad format. In each case, a planarizingpad and a planarizing solution are combined to define a planarizingmedium that mechanically and/or chemically-mechanically removes materialfrom the surface of a substrate. The planarizing pad may be of afixed-abrasive or non-abrasive type. With a fixed-abrasive pad type,abrasive particles are fixedly bonded to a suspension material.Furthermore, the planarizing solution used with a fixed-abrasive padtype is typically a “clean” solution, i.e., substantially devoid ofabrasive particles as such abrasive particles are fixedly distributedacross a planarizing surface of the planarizing pad. With a non-abrasiveplanarizing pad, no abrasive particles are associated with the pad, sothe abrasive particles are introduced in the planarizing solution. Suchplanarizing solutions for use with non-abrasive pad types are oftenslurries of both abrasive particles as well as chemicals to aid removalof material from a substrate.

To planarize the substrate with the planarizing machine, the surface ofthe substrate is first contacted against the planarizing pad in thepresence of the planarizing solution, i.e., a planarizing surface of theplanarizing medium. While in contact, the substrate is then movedrelative to the planarizing surface of the planarizing medium, generallythrough lateral, rotational, revolving or orbital movement of thesubstrate, the planarizing pad or both. Lateral movement is defined asmovement in one direction. Rotational movement is defined as rotationabout an axis located at the center point of the object in motion.Revolving movement is defined as rotation about some axis located atother than the center point of the object in motion. Orbital movement isdefined as rotational or revolving movement combined with oscillation.Different types of movement may be combined, e.g., rotational movementof the substrate and rotational movement of the planarizing pad orrevolving and rotational movement of the substrate against a stationaryplanarizing pad. As is well understood in the art, such relativemovement is in a plane substantially parallel to the surface ofsubstrate. As a result, the abrasive particles and/or the chemicals inthe planarizing medium remove material from the surface of thesubstrate.

Fixed abrasive pad types are well known in the art of semiconductorwafer processing. See, e.g., U.S. Pat. No. 5,692,950 issued Dec. 2, 1997to Rutherford et al.; U.S. Pat. No. 5,624,303 issued Apr. 29, 1997 toRobinson; and U.S. Pat. No. 5,335,453 issued Aug. 9, 1994 to Baldy etal. Despite widespread recognition and acceptance of fixed abrasive padsin the processing of semiconductor wafers, effective planarizingsolutions for use in the fixed-abrasive planarization of an advantageousbarrier material and conductor, i.e., titanium nitride (TiN), arelacking. As a result, the customary processing for planarizing titaniumnitride utilizes abrasive slurries with non-abrasive pad types.

One problem with CMP processing is that the planarized surface of thewafer may not be sufficiently uniform across the whole surface of thewafer. In the competitive semiconductor industry, it is also desirableto maximize the throughput of finished wafers. The uniformity of theplanarized surface and maximization of throughput is a function of theeffectiveness and repeatability of the planarizing solution utilizedwith the planarizing pad, as well as a wide array of other CMP operatingparameters. While a wide variety of planarizing solutions are available,these solutions are generally specific to the composition of thematerial to be removed as well as the type of planarizing pad used. Forobvious reasons, planarizing solutions developed for non-abrasive padtypes are ill suited for use with fixed-abrasive pad types. Therefore,it would be desirable to develop effective planarizing solutions forplanarization of titanium nitride on the surface of a semiconductorwafer for use in conjunction with fixed-abrasive planarizing pads.

For the reasons stated above, and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art formethods of planarizing titanium nitride using fixed-abrasive planarizingpads.

SUMMARY

Embodiments of titanium nitride layers planarized in accordance with theinvention may be utilized in the production of integrated circuits, andvarious apparatus utilizing such integrated circuits. Planarizingsolutions may be used for removing titanium nitride from the surface ofa substrate using a fixed-abrasive planarizing pad. The planarizingsolutions take the form of an etchant solution or an oxidizing solution.The etchant solutions are aqueous solutions containing an etchant and abuffer. The etchant contains one or more etching agents selective totitanium nitride. The oxidizing solutions are aqueous solutionscontaining an oxidizer and a buffer. The oxidizer contains one or moreoxidizing agents selective to titanium nitride. In either solution,i.e., etchant or oxidizing solution, the buffer contains one or morebuffering agents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B are a cross-sectional views of a substrate with a titaniumnitride layer at sequential processing stages in accordance with anembodiment of the invention.

FIG. 2A is a schematic of a web-format planarizing machine as used inaccordance with an embodiment of the invention.

FIG. 2B is a schematic of a fixed-pad format planarizing machine as usedin accordance with an embodiment of the invention.

FIG. 3 is a block diagram of an integrated circuit memory device inaccordance with an embodiment of the invention.

FIG. 4 is an elevation view of a wafer containing semiconductor dies inaccordance with an embodiment of the invention.

FIG. 5 is a block diagram of an exemplary circuit module in accordancewith an embodiment of the invention.

FIG. 6 is a block diagram of an exemplary memory module in accordancewith an embodiment of the invention.

FIG. 7 is a block diagram of an exemplary electronic system inaccordance with an embodiment of the invention.

FIG. 8 is a block diagram of an exemplary memory system in accordancewith an embodiment of the invention.

FIG. 9 is a block diagram of an exemplary computer system in accordancewith an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which is shown by way of illustration specific embodiments inwhich the inventions may be practiced. These embodiments are describedin sufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that process or mechanical changes may be made withoutdeparting from the scope of the present invention. The terms wafer andsubstrate used previously and in the following description include anybase semiconductor structure. Both are to be understood as includingsilicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI)technology, thin film transistor (TFT) technology, doped and undopedsemiconductors, epitaxial layers of silicon supported by a basesemiconductor, as well as other semiconductor structures well known toone skilled in the art. Furthermore, when reference is made to a waferor substrate in the following description, previous process steps mayhave been utilized to form regions/junctions in the base semiconductorstructure. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined only by the appended claims.

In one embodiment, the invention provides a method of planarizingtitanium nitride on a surface of a substrate. The method includescontacting the surface of the substrate with a planarizing surface of aplanarizing medium, the planarizing medium comprising a fixed-abrasiveplanarizing pad and a clean planarizing solution. The method furtherincludes moving the surface of the substrate relative to the planarizingsurface of the planarizing medium, thereby abrading the titanium nitrideon the surface of the substrate. In another embodiment, moving thesurface of the substrate relative to the planarizing surface of theplanarizing medium comprises moving at least one of the substrate andthe planarizing surface of the planarizing medium in a manner selectedfrom the group consisting of lateral, rotational, revolving and orbital.In a further embodiment, the planarizing solution is an etchantsolution. In a still further embodiment, the planarizing solution is anoxidizing solution.

In another embodiment, a method of planarizing titanium nitride on asurface of a substrate includes use of an etchant solution as theplanarizing solution, wherein the etchant solution contains an etchantand a buffer in aqueous solution. In one embodiment, the etchantcomprises at least one etching agent selected from the group consistingof oxalic acid, ascorbic acid and phosphoric acid. In a furtherembodiment, the buffer comprises at least one buffering agent selectedfrom the group consisting of ammonium acetate, ammonium oxalate,ammonium phosphate and diammonium phosphate. In a still furtherembodiment, the etchant solution has a pH of approximately 1 to 5. Inyet another embodiment, the etchant solution has a pH of approximately1.5 to 3.

In a further embodiment, a method of planarizing titanium nitride on asurface of a substrate includes use of an oxidizing solution as theplanarizing solution, wherein the oxidizing solution contains anoxidizer and a buffer in aqueous solution. In one embodiment, theoxidizer comprises at least one oxidizing agent selected from the groupconsisting of ammonium persulfate, ammonium heptamolybdate, cericammonium nitrate, ceric ammonium sulfate and hydrogen peroxide. Inanother embodiment, the buffer comprises at least one buffering agentselected from the group consisting of phosphoric acid, ammonium acetate,ammonium oxalate, ammonium phosphate and diammonium phosphate. In yetanother embodiment, the oxidizing solution has a pH of approximately 1to 6. In a further embodiment, the oxidizing solution has a pH ofapproximately 1.5 to 4.

In one embodiment, the invention provides a method of planarizingtitanium nitride on a surface of a substrate. The method includescontacting the surface of the substrate with a planarizing surface of aplanarizing medium, the planarizing medium comprising a fixed-abrasiveplanarizing pad and a clean planarizing solution, wherein theplanarizing solution is an aqueous solution comprising approximately 1%to 5% by weight of oxalic acid and approximately 2% to 10% by weight ofammonium acetate. The method further includes moving the surface of thesubstrate relative to the planarizing surface of the planarizing medium,thereby abrading the titanium nitride on the surface of the substrate.

In another embodiment, the invention provides a clean aqueousplanarizing solution. The clean aqueous planarizing solution includes anetchant having at least one etching agent selected from the groupconsisting of oxalic acid, ascorbic acid and phosphoric acid, and abuffer. In one embodiment, the buffer comprises at least one bufferingagent selected from the group consisting of ammonium acetate, ammoniumoxalate, ammonium phosphate and diammonium phosphate. In a furtherembodiment, the planarizing solution has a pH of approximately 1 to 5.In a still further embodiment, the planarizing solution has a pH ofapproximately 1.5 to 3. In another embodiment, the planarizing solutionhas approximately 1% to 10% by weight of the etchant and approximately0% to 10% by weight of the buffer. In yet another embodiment, theplanarizing solution has approximately 1% to 5% by weight of the etchantand approximately 0% to 10% by weight of the buffer. In anotherembodiment, the planarizing solution has approximately 1% to 5% byweight of oxalic acid and approximately 2% to 10% by weight of ammoniumacetate.

In a further embodiment, the invention provides a clean aqueousplanarizing solution. The clean aqueous planarizing solution includes anoxidizer having at least one oxidizing agent selected from the groupconsisting of ammonium persulfate, ammonium heptamolybdate, cericammonium nitrate, ceric ammonium sulfate and hydrogen peroxide, and abuffer. In one embodiment, the buffer comprises at least one bufferingagent selected from the group consisting of phosphoric acid, ammoniumacetate, ammonium oxalate, ammonium phosphate and diammonium phosphate.In another embodiment, the planarizing solution has a pH ofapproximately 1 to 6. In yet another embodiment, the planarizingsolution has a pH of approximately 1.5 to 4. In a further embodiment,the planarizing solution has approximately 1% to 10% by weight of theoxidizer and approximately 0% to 10% by weight of the buffer. In a stillfurther embodiment, the planarizing solution has approximately 1% to 5%by weight of the oxidizer and approximately 0.5% to 3% by weight of thebuffer.

Further embodiments of the invention provide planarizing solutions andmethods of removing titanium nitride of varying scope. Still furtherembodiments of the invention provide apparatus of varying scope producedin accordance with methods and planarizing solutions of the invention.

FIG. 1A illustrates a typical substrate 12 having a first layer 1 and apatterned second layer 2. In typical semiconductor processing, firstlayer 1 may represent a wafer of single-crystal silicon or other basesemiconductor layer, an insulating layer separating second patternedlayer 2 from other layers, or a combination of multiple layers formed inprior processing steps. The composition and structure of first layer 1and patterned second layer 2 are trivial.

A titanium nitride layer 3 is formed on a portion of first layer 1exposed by patterned second layer 2. Titanium nitride layer 3 may beformed by chemical vapor deposition (CVD) or other processes well knownin the art. In FIG. 1B, a CMP process in accordance with an embodimentof the invention is used to remove a portion of titanium nitride layer 3and to planarize the surface of substrate 12. Titanium nitride layer 3may be utilized as a contact in an integrated circuit, e.g., where theportion of first layer 1 exposed by patterned second layer 1 forms anactive area of a semiconductor device. The integrated circuit may beutilized in the formation of various electronic devices.

FIG. 2A illustrates a web-format planarizing machine 10 for planarizinga substrate 12 in accordance with an embodiment of the invention. Thesubstrate 12 has titanium nitride on its surface as illustrated in FIG.1A. Planarizing machine 10 is used to remove at least a portion of thetitanium nitride and to planarize the surface of substrate 12.

The planarizing machine 10 has a support table 14 with a top-panel 16 ata workstation where an operative portion (A) of a planarizing pad 40 ispositioned. The top-panel 16 is generally a rigid plate to provide aflat, solid surface to which a particular section of the planarizing pad40 may be secured during planarization.

The planarizing machine 10 also has a plurality of rollers to guide,position and hold the planarizing pad 40 over the top-panel 16. Therollers include a supply roller 20, first and second idler rollers 21 aand 21 b, first and second guide rollers 22 a and 22 b, and a take-uproller 23. The supply roller 20 carries an unused or pre-operativeportion of the planarizing pad 40, and the take-up roller 23 carries aused or post-operative portion of the planarizing pad 40. Additionally,the first idler roller 21 a and the first guide roller 22 a stretch theplanarizing pad 40 over the top-panel 16 to hold the planarizing pad 40stationary during operation. A motor (not shown) drives at least one ofthe supply roller 20 and the take-up roller 23 to sequentially advancethe planarizing pad 40 across the top-panel 16. As such, cleanpre-operative sections of the planarizing pad 40 may be quicklysubstituted for used sections to provide a consistent surface forplanarizing and/or cleaning the substrate 12.

The web-format planarizing machine 10 also has a carrier assembly 30that controls and protects the substrate 12 during planarization. Thecarrier assembly 30 generally has a substrate holder 32 to pick up, holdand release the substrate 12 at appropriate stages of the planarizingcycle. A plurality of nozzles 33 attached to the substrate holder 32dispense a planarizing solution 44 onto a planarizing surface 42 of theplanarizing pad 40. The carrier assembly 30 also generally has a supportgantry 34 carrying a drive assembly 35 that translates along the gantry34. The drive assembly 35 generally has a actuator 36, a drive shaft 37coupled to the actuator 36, and an arm 38 projecting from the driveshaft 37. The arm 38 carries the substrate holder 32 via another shaft39 such that the drive assembly 35 revolves the substrate holder 32about an axis B-B offset from a center point C-C of the substrate 12.

The planarizing pad 40 and the planarizing solution 44 define aplanarizing medium, having the planarizing surface 42, thatchemically-mechanically removes material from the surface of thesubstrate 12. The planarizing pad 40 is of a fixed-abrasive type.

In one embodiment, the planarizing solution 44 is an etchant solutionand contains an etchant of at least one etching agent and a buffer of atleast one buffering agent in aqueous solution. Etchant chemistriesdiffer significantly from oxidizer chemistries commonly used inconventional abrasive slurries, i.e., those used with non-abrasive padtypes. In etchant chemistries, the etchants are reducing agents whichcomplex the titanium to facilitate removal. Preferred etching agentsinclude oxalic acid (HOOCCOOH.2H₂O), ascorbic acid (C₆H₈O₆), andphosphoric acid (H₃PO₄). Preferred buffering agents include ammoniumacetate (NH₄(C₂H₃O₂)), ammonium oxalate ((NH₄)₂C₂O₄H₂O), ammoniumphosphate (NH₄H₂PO₄), and diammonium phosphate ((NH₄)₂HPO₄).

The etchant solution has a pH of approximately 1 to 5, preferably lessthan approximately 3, and more preferably in the range of approximately1.5 to 3. Etchant concentration in the etchant solution is preferably inthe range of approximately 1% to 10% by weight and more preferably inthe range of approximately 1% to 5% by weight.

Suitable buffer concentrations are expected to be in the range ofapproximately 0% to 10% by weight. Concentrations of etchant and buffermay fall outside the preferred ranges depending upon the combination ofetching agents and buffering agents selected. However, it is within theskill in the art to determine appropriate concentrations without undueexperimentation to achieve the desired pH ranges. The pH is defined bythe equation pH=log₁₀[H+]⁻¹, the logarithm of the reciprocal of thehydrogen-ion concentration of the solution.

In one embodiment, more than one etching agent is used as the etchant inthe etchant solution. In another embodiment, the etchant in the etchantsolution consists essentially of one etching agent. In one embodiment,more than one buffering agent is used as the buffer in the etchantsolution. In another embodiment, the buffer in the etchant solutionconsists essentially of one buffering agent. In still anotherembodiment, planarizing solution 44 comprises an aqueous solution havingapproximately 1% to 5% by weight of oxalic acid, approximately 2% to 10%by weight of ammonium acetate, and a pH of approximately 1.5 to 3.

The etchant solution may contain additional chemical components that donot materially affect the basic and novel characteristic of thesolutions disclosed herein. Some examples include dyes, lubricants,stabilizers, surfactants, thickening agents, preservatives andantimicrobial agents to name a few. Where more than one etching agent isutilized in the etchant solution, the weight % of the etchant is basedon the combined weight of all such etching agents in relation to thetotal weight of the solution. Where more than one buffering agent isutilized in the etchant solution, the weight % of the buffer is based onthe combined weight of all such buffering agents in relation to thetotal weight of the solution.

In a further embodiment, the planarizing solution 44 is an oxidizingsolution and contains an oxidizer of at least one oxidizing agent and abuffer of at least one buffering agent in aqueous solution. Preferredoxidizing agents include ammonium persulfate ((NH₄)₂S₂O₈), ammoniumheptamolybdate ((NH₄)₆Mo₇O₂₄.4H₂O), ceric ammonium nitrate(Ce(NO₃)₄.2NH₄NO₃), ceric ammonium sulfate (Ce(SO₄)₂.2(NH₄)₂SO₄), andhydrogen peroxide (H₂O₂). Preferred buffering agents include phosphoricacid (H₃PO₄), ammonium acetate (NH₄(C₂H₃O₂)), ammonium oxalate((NH₄)₂C₂O₄.H₂O), ammonium phosphate (NH₄H₂PO₄), and diammoniumphosphate ((NH₄)₂HPO₄).

The oxidizing solution has a pH of approximately 1 to 6, preferably lessthan approximately 4, and more preferably in the range of approximately1.5 to 4. Oxidizer concentration in the oxidizing solution is preferablyin the range of approximately 1% to 10% by weight and more preferably inthe range of approximately 1% to 5% by weight. An oxidizer concentrationof approximately 2% by weight is further preferred.

Suitable buffer concentrations are expected to be in the range ofapproximately 0% to 10% by weight. Such concentration of buffer isgenerally expected to be approximately 0.5% to 3% by weight at thepreferred oxidizer concentrations. Concentrations of oxidizer and buffermay fall outside the preferred ranges depending upon the combination ofoxidizing agents and buffering agents selected. However, it is withinthe skill in the art to determine appropriate concentrations withoutundue experimentation to achieve the desired pH ranges.

In one embodiment, more than one oxidizing agent is used as the oxidizerin the oxidizing solution. In another embodiment, the oxidizer in theoxidizing solution consists essentially of one oxidizing agent. In oneembodiment, more than one buffering agent is used as the buffer in theoxidizing solution. In another embodiment, the buffer in the oxidizingsolution consists essentially of one buffering agent.

The oxidizing solution may contain additional chemical components thatdo not materially affect the basic and novel characteristic of thesolutions disclosed herein. Some examples include dyes, lubricants,stabilizers, surfactants, thickening agents, preservatives andantimicrobial agents to name a few. Where more than one oxidizing agentis utilized in the oxidizing solution, the weight % of the oxidizer isbased on the combined weight of all such oxidizing agents in relation tothe total weight of the solution. Where more than one buffering agent isutilized in the oxidizing solution, the weight % of the buffer is basedon the combined weight of all such buffering agents in relation to thetotal weight of the solution.

To planarize the substrate 12 with the planarizing machine 10, thecarrier assembly 30 presses the substrate 12 against the planarizingsurface 42 of the planarizing pad 40 in the presence of the planarizingsolution 44. The drive assembly 35 then moves the substrate holder 32relative to the planarizing surface 42 to move the substrate 12 acrossthe planarizing surface 42. Movement of the substrate holder 32 is in aplane substantially parallel to the surface of substrate 12. As thesurface of the substrate 12 moves across the planarizing surface 42,material is continuously removed from the surface of the substrate 12through abrasion.

Alternatively, the planarizing machine may utilize fixed pads instead ofwebs as the planarization pad. FIG. 2B illustrates a fixed-pad formatplanarizing machine 100 for use in accordance with an embodiment of theinvention. The planarizing machine 100 has a platen 120, an underpad 125attached to the platen 120, a polishing pad 140 attached to the underpad125, and a carrier assembly 130 positioned over the polishing pad 140. Adrive assembly 126 rotates the platen 120 (as indicated by arrow A), orit reciprocates the platen 120 back and forth (as indicated by arrow B).Other planarizing machines may revolve the platen 120 about a point.Since the polishing pad 140 is attached to the underpad 125, thepolishing pad 140 moves with the platen 120.

The carrier assembly 130 has a substrate holder 131 and resilient pad134 to which a substrate 12 may be attached. The carrier assembly 130may be a weighted, free-floating substrate holder, or an actuatorassembly 136 may be attached to the carrier assembly 130 to impart axialand/or rotational motion (as indicated by arrows C and D, respectively).

To planarize the substrate 12 with the planarizing machine 100, thecarrier assembly 130 presses the substrate 12 surface-downward againstthe polishing pad 140. While the surface of the substrate 12 pressesagainst the polishing pad 140, at least one of the platen 120, andtherefore the planarizing surface 142, or the substrate holder 131 movesrelative to the other to move the substrate 12 across the planarizingsurface 142. Movement of the platen 120 and/or the substrate holder 131are in planes substantially parallel to the surface of substrate 12. Asthe surface of the substrate 12 moves across the planarizing surface142, material is continuously removed from the surface of the substrate12 through abrasion.

The planarizing pad 140 and the planarizing solution 44 define aplanarizing medium that chemically-mechanically removes material fromthe surface of the substrate 12. The planarizing pad 140 is of afixed-abrasive type. The planarizing machine 100 has a planarizingsolution dispenser 150 for application of the planarizing solution 44 tothe planarizing surface 142 of the planarizing medium. Planarizingsolution 44 may be an oxidizing solution or an etchant solution of theinvention.

It is recognized that the planarizing machines described above aretypical of the major formats, i.e., web format or fixed-pad format, butthat other mechanical variations and adaptations are well known in theart. However, planarizing solutions of the invention are not dependentupon the planarizing machine format.

The various embodiments of the invention permit CMP removal of titaniumnitride using fixed-abrasive planarizing pads, regardless of the formatof the planarizing machine. In conjunction with the various embodimentsof the invention, the CMP process may be a conditionless planarizingprocess, i.e., conditioning of the planarizing pad prior to use may beeliminated.

It will be apparent that semiconductor wafers processed in accordancewith the invention may be utilized to produce a variety of integratedcircuit devices. It is believed that integrated circuit devices producedin accordance with the invention exhibit less performance variabilitythan devices produced using non-abrasive pad types with abrasive slurryplanarizing solutions due to reduced process variability. The reducedprocess variability arises from the ability to eliminate conditioning ofthe planarizing pad prior to use as well as elimination of variabilityassociated with the propensity of the abrasive particles in abrasiveslurry planarizing solutions to settle or agglomerate during storage anduse.

Consequently, integrated circuit devices produced in accordance with theinvention are expected to exhibit physical characteristics differentfrom the physical characteristics inherent in planarizing titaniumnitride using non-abrasive planarizing pads in conjunction with abrasiveslurry planarizing solutions due to more uniform abrasion of thetitanium nitride on the surface of the substrate. In addition, reactivecharacteristics inherent in the planarizing solutions of the inventionare expected to produce physical characteristics different from thephysical characteristics produced by planarizing solutions of alternatechemistries, given the differing reactive characteristics inherent insuch alternate chemistries. One typical integrated circuit device foruse with the invention is a memory device.

Memory Devices

FIG. 3 is a simplified block diagram of a memory device according to oneembodiment of the invention. The memory device 300 includes an array ofmemory cells 302, address decoder 304, row access circuitry 306, columnaccess circuitry 308, control circuitry 310, and Input/Output circuit312. The memory can be coupled to an external microprocessor 314, ormemory controller for memory accessing. The memory receives controlsignals from the processor 314, such as WE*, RAS* and CAS* signals. Thememory is used to store data which is accessed via I/O lines. It will beappreciated by those skilled in the art that additional circuitry andcontrol signals can be provided, and that the memory device of FIG. 3has been simplified to help focus on the invention. The memory device300 has at least one titanium nitride layer planarized in accordancewith the invention.

It will be understood that the above description of a DRAM (DynamicRandom Access Memory) is intended to provide a general understanding ofthe memory and is not a complete description of all the elements andfeatures of a DRAM. Further, the invention is equally applicable to anysize and type of memory circuit and is not intended to be limited to theDRAM described above. Other alternative types of devices include SRAM(Static Random Access Memory) or Flash memories. Additionally, the DRAMcould be a synchronous DRAM commonly referred to as SGRAM (SynchronousGraphics Random Access Memory), SDRAM (Synchronous Dynamic Random AccessMemory), SDRAM II, and DDR SDRAM (Double Data Rate SDRAM), as well asSynchlink or Rambus DRAMs.

As recognized by those skilled in the art, memory devices of the typedescribed herein are generally fabricated as an integrated circuitcontaining a variety of semiconductor devices. The integrated circuit issupported by a substrate. Integrated circuits are typically repeatedmultiple times on each substrate. The substrate is further processed toseparate the integrated circuits into dies as is well known in the art.

Semiconductor Dies

With reference to FIG. 4, in one embodiment, a semiconductor die 710 isproduced from a silicon wafer 700. A die is an individual pattern,typically rectangular, on a substrate that contains circuitry, orintegrated circuit devices, to perform a specific function.Semiconductor die 710 has at least one titanium nitride layer planarizedin accordance with the invention. A semiconductor wafer will typicallycontain a repeated pattern of such dies containing the samefunctionality. Die 710 may contain circuitry for the inventive memorydevice, as discussed above. Die 710 may further contain additionalcircuitry to extend to such complex devices as a monolithic processorwith multiple functionality. Die 710 is typically packaged in aprotective casing (not shown) with leads extending therefrom (not shown)providing access to the circuitry of the die for unilateral or bilateralcommunication and control.

Circuit Modules

As shown in FIG. 5, two or more dies 710 may be combined, with orwithout protective casing, into a circuit module 800 to enhance orextend the functionality of an individual die 710. Circuit module 800may be a combination of dies 710 representing a variety of functions, ora combination of dies 710 containing the same functionality. Someexamples of a circuit module include memory modules, device drivers,power modules, communication modems, processor modules andapplication-specific modules and may include multilayer, multichipmodules. Circuit module 800 may be a subcomponent of a variety ofelectronic systems, such as a clock, a television, a cell phone, apersonal computer, an automobile, an industrial control system, anaircraft and others. Circuit module 800 will have a variety of leads 810extending therefrom and coupled to the dies 710 providing unilateral orbilateral communication and control.

FIG. 6 shows one embodiment of a circuit module as memory module 900.Memory module 900 generally depicts a Single Inline Memory Module (SIMM)or Dual Inline Memory Module (DIMM). A SIMM or DIMM is generally aprinted circuit board (PCB) or other support containing a series ofmemory devices. While a SIMM will have a single in-line set of contactsor leads, a DIMM will have a set of leads on each side of the supportwith each set representing separate I/O signals. Memory module 900contains multiple memory devices 910 contained on support 915, thenumber depending upon the desired bus width and the desire for parity.Memory module 900 may contain memory devices 910 on both sides ofsupport 915. Memory module 900 accepts a command signal from an externalcontroller (not shown) on a command link 920 and provides for data inputand data output on data links 930. The command link 920 and data links930 are connected to leads 940 extending from the support 915. Leads 940are shown for conceptual purposes and are not limited to the positionsshown in FIG. 6.

Electronic Systems

FIG. 7 shows an electronic system 1000 containing one or more circuitmodules 800. Electronic system 1000 generally contains a user interface1010. User interface 1010 provides a user of the electronic system 1000with some form of control or observation of the results of theelectronic system 1000. Some examples of user interface 1010 include thekeyboard, pointing device, monitor and printer of a personal computer;the tuning dial, display and speakers of a radio; the ignition switchand gas pedal of an automobile; and the card reader, keypad, display andcurrency dispenser of an automated teller machine. User interface 1010may further describe access ports provided to electronic system 1000.Access ports are used to connect an electronic system to the moretangible user interface components previously exemplified. One or moreof the circuit modules 800 may be a processor providing some form ofmanipulation, control or direction of inputs from or outputs to userinterface 1010, or of other information either preprogrammed into, orotherwise provided to, electronic system 1000. As will be apparent fromthe lists of examples previously given, electronic system 1000 willoften contain certain mechanical components (not shown) in addition tocircuit modules 800 and user interface 1010. It will be appreciated thatthe one or more circuit modules 800 in electronic system 1000 can bereplaced by a single integrated circuit. Furthermore, electronic system1000 may be a subcomponent of a larger electronic system.

FIG. 8 shows one embodiment of an electronic system as memory system1100. Memory system 1100 contains one or more memory modules 900 and amemory controller 1110. Memory controller 1110 provides and controls abidirectional interface between memory system 1100 and an externalsystem bus 1120. Memory system 1100 accepts a command signal from theexternal bus 1120 and relays it to the one or more memory modules 900 ona command link 1130. Memory system 1100 provides for data input and dataoutput between the one or more memory modules 900 and external systembus 1120 on data links 1140.

FIG. 9 shows a further embodiment of an electronic system as a computersystem 1200. Computer system 1200 contains a processor 1210 and a memorysystem 1100 housed in a computer unit 1205. Computer system 1200 is butone example of an electronic system containing another electronicsystem, i.e., memory system 1100, as a subcomponent. Computer system1200 optionally contains user interface components. Depicted in FIG. 9are a keyboard 1220, a pointing device 1230, a monitor 1240, a printer1250 and a bulk storage device 1260. It will be appreciated that othercomponents are often associated with computer system 1200 such asmodems, device driver cards, additional storage devices, etc. It willfurther be appreciated that the processor 1210 and memory system 1100 ofcomputer system 1200 can be incorporated on a single integrated circuit.Such single package processing units reduce the communication timebetween the processor and the memory circuit.

CONCLUSION

Planarizing solutions, and their methods of use, for removing titaniumnitride from the surface of a substrate using a fixed-abrasiveplanarizing pad type are disclosed. The planarizing solutions may takethe form of an etchant solution or an oxidizing solution. The etchantsolutions are aqueous solutions containing an etchant and a buffer. Theetchant contains one or more etching agents selective to titaniumnitride. The oxidizing solutions are aqueous solutions containing anoxidizer and a buffer. The oxidizer contains one or more oxidizingagents selective to titanium nitride. In either solution, i.e., etchantor oxidizing solution, the buffer contains one or more buffering agents.Titanium nitride layers planarized in accordance with the invention maybe utilized in the production of integrated circuits, and variousapparatus utilizing such integrated circuits.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. Many adaptations ofthe invention will be apparent to those of ordinary skill in the art.For example, other planarizing machine formats may be utilized with theinvention. Furthermore, titanium nitride layers planarized in accordancewith the invention may be utilized as conductor lines, barrier layers orother structures in addition to the contacts described herein.Accordingly, this application is intended to cover any adaptations orvariations of the invention. It is manifestly intended that thisinvention be limited only by the following claims and equivalentsthereof.

1. An electronic system, comprising: a processor; and a circuit modulehaving a plurality of leads coupled to the processor, and further havinga semiconductor die coupled to at least a portion of the plurality ofleads, wherein the semiconductor die comprises: a substrate; and anintegrated circuit supported by the substrate and having a titaniumnitride layer, wherein the titanium nitride layer is planarized by amethod comprising: abrading the titanium nitride layer with aplanarizing surface of a planarizing medium comprising a fixed-abrasiveplanarizing pad and a clean planarizing solution.
 2. The electronicsystem of claim 1, wherein the planarizing solution is an aqueousetchant solution comprising an etchant and a buffer, wherein the etchantcomprises at least one etching agent selected from the group consistingof oxalic acid, ascorbic acid and phosphoric acid.
 3. The electronicsystem of claim 2, wherein the buffer comprises at least one bufferingagent selected from the group consisting of ammonium acetate, ammoniumoxalate, ammonium phosphate and diammonium phosphate.
 4. The electronicsystem of claim 2, wherein the planarizing solution has a pH ofapproximately 1 to
 5. 5. The electronic system of claim 1, wherein theplanarizing solution is an aqueous oxidizing solution comprising anoxidizer and a buffer, wherein the oxidizer comprises at least oneoxidizing agent selected from the group consisting of ammoniumpersulfate, ammonium heptamolybdate, ceric ammonium nitrate, cericammonium sulfate and hydrogen peroxide.
 6. The electronic system ofclaim 5, wherein the buffer comprises at least one buffering agentselected from the group consisting of phosphoric acid, ammonium acetate,ammonium oxalate, ammonium phosphate and diammonium phosphate.
 7. Theelectronic system of claim 5, wherein the planarizing solution has a pHof approximately 1 to
 6. 8. The electronic system of claim 1, whereinthe planarizing solution is an aqueous solution comprising approximately1% to 5% by weight of oxalic acid and approximately 2% to 10% by weightof ammonium acetate.
 9. The electronic system of claim 2, wherein theplanarizing solution further includes a thickening agent.
 10. Theelectronic system of claim 5, wherein the planarizing solution furtherincludes a thickening agent.
 11. An electronic system, comprising: aprocessor; and a circuit module having a plurality of leads coupled tothe processor, and further having a semiconductor die coupled to atleast a portion of the plurality of leads, the semiconductor diecomprising: a substrate; and an integrated circuit supported by thesubstrate and having a titanium nitride layer, the titanium nitridelayer planarized by a method comprising: abrading the titanium nitridelayer with a planarizing surface of a planarizing medium comprising afixed-abrasive planarizing pad and a clean planarizing solution, theplanarizing solution having an oxidizer and a buffer, the planarizingsolution being approximately 1% to 10% by weight of the oxidizer andapproximately 0% to 10% by weight of the buffer.
 12. The electronicsystem of claim 11, wherein the oxidizer comprises at least oneoxidizing agent selected from the group consisting of ammoniumpersulfate, ammonium heptamolybdate, ceric ammonium nitrate, cericammonium sulfate and hydrogen peroxide.
 13. The electronic system ofclaim 11, wherein the oxidizing solution has a pH of approximately 1.5to
 4. 14. An electronic system, comprising: a processor; and a circuitmodule having a plurality of leads coupled to the processor, and furtherhaving a semiconductor die coupled to at least a portion of theplurality of leads, the semiconductor die comprising: a substrate; andan integrated circuit supported by the substrate and having a titaniumnitride layer, the titanium nitride layer planarized by a methodcomprising: abrading the titanium nitride layer with a planarizingsurface of a planarizing medium including a fixed-abrasive planarizingpad and a clean planarizing solution, the planarizing solution having anetchant, the etchant including at least one etching agent selected fromthe group consisting of oxalic acid, ascorbic acid and phosphoric acid,the planarizing solution having approximately 1% to 5% by weight of theetchant.
 15. The electronic system of claim 14, the planarizing solutionfurther includes a buffer, the buffer having at least one bufferingagent selected from the group consisting of ammonium acetate, ammoniumoxalate, ammonium phosphate and diammonium phosphate.
 16. The electronicsystem of claim 14, wherein the planarizing solution has a pH less thanapproximately
 3. 17. An electronic system, comprising: a processor; anda circuit module having a plurality of leads coupled to the processor,and further having a semiconductor die coupled to at least a portion ofthe plurality of leads, the semiconductor die comprising: a substrate;and an integrated circuit supported by the substrate and having atitanium nitride layer, the titanium nitride layer planarized by amethod comprising: abrading the titanium nitride layer with aplanarizing surface of a planarizing medium including a fixed-abrasiveplanarizing pad and a clean planarizing solution, the planarizingsolution having an etchant, the etchant including one etching agentselected from the group consisting of oxalic acid, ascorbic acid andphosphoric acid.
 18. The electronic system of claim 17, wherein theplanarizing solution further includes a buffer, the buffer having atleast one buffering agent selected from the group consisting of ammoniumacetate, ammonium oxalate, ammonium phosphate and diammonium phosphate.19. The electronic system of claim 18, wherein the planarizing solutionis approximately 1% to 10% by weight of the etchant and approximately 0%to 10% by weight of the buffer.
 20. An electronic system, comprising: aprocessor; and a circuit module having a plurality of leads coupled tothe processor, and further having a semiconductor die coupled to atleast a portion of the plurality of leads, the semiconductor diecomprising: a substrate; and an integrated circuit supported by thesubstrate and having a titanium nitride layer, the titanium nitridelayer planarized by a method comprising: abrading the titanium nitridelayer with a planarizing surface of a planarizing medium including afixed-abrasive planarizing pad and a clean planarizing solution, theplanarizing solution having an oxidizer, the oxidizer including oneoxidizing agent selected from the group consisting of ammoniumpersulfate, ammonium heptamolybdate, ceric ammonium nitrate, cericammonium sulfate and hydrogen peroxide.
 21. The electronic system ofclaim 20, wherein the planarizing solution further includes a buffer,the buffer having at least one buffering agent selected from the groupconsisting of ammonium acetate, ammonium oxalate, ammonium phosphate anddiammonium phosphate.
 22. The electronic system of claim 21, wherein theplanarizing solution is approximately 2% by weight of the oxidizer.